As one conventional example of a refrigeration apparatus for performing a multi-stage compression-type refrigeration cycle having a refrigerant circuit which can switch between a cooling operation and a heating operation and which is capable of intermediate pressure injection, Japanese Laid-open Patent Application No. 2007-232263 discloses an air-conditioning apparatus for performing a two-stage compression-type refrigeration cycle having a refrigerant circuit which can switch between an air-cooling operation and an air-warming operation and which is capable of intermediate pressure injection. This air-conditioning apparatus has primarily a compressor having two compression elements, one first-stage and one second-stage, connected in series, a four-way switching valve, an outdoor heat exchanger, an indoor heat exchanger, and a second-stage injection tube for returning to the second-stage compression element some of the refrigerant whose heat has been radiated in the outdoor heat exchanger or the indoor heat exchanger.